Latex allergy is recognized as a serious health problem among health care workers and children with spina bifida. The identification and characterization of major allergens in latex will form a basis from which test reagents can be developed. Recently a high percentage of latex allergy patients have been reported to also have food allergy. Fruits frequently have been reported to have cross-reactivities with latex including chestnut, banana, papaya and kiwifruit. The homologies between latex allergens and proteins from fruits will aid in our understanding of the molecular mechanism in the cross-reactivities between latex and food allergy. A number of IgE-reactive proteins have been identified in natural and processed latex products. One of the most acidic proteins in the cytoplasm of lacticifer cells of rubber trees is demonstrated to be a potent allergen in eliciting allergenic reactions in humans. This acidic protein, Hev b 5 was found in extracts prepared from many brands of gloves. The purified protein elicits histamine release from passively sensitized human basophils. From a latex cDNA library the cDNA coding for this protein was isolated and sequenced. The deduced amino acid sequence shows a high degree of homoloty to an acidic protein in kiwifruit. The sequence homology between these two acidic proteins provided a molecular explanation for the high frequence of fruit hypersensitivity in latex allergic patients.